The purpose of 'Booth Babes' is to attract customers, presumably men to the booth. Whether this is an effective strategy is a separate discussion.
It's human nature, and attempts to circumvent it are trivially overcome.
Exhibitors that are currently using this approach can hire the same models and dress them in 'Business-appropriate' attire. The end result is you will still have beautiful women (who may know nothing about the product) staffing a booth and bringing in men.
If anything, this will provide more plausible deniability for more image-conscious men who don't wish to be seen chatting up some lyra- and latex- clad contractor at a booth.
I suppose if that become too troublesome, they can always ban makeup or attractive staffers (of both sexes). Or require that contractors be able to talk knowledgeably about the product.
I'm not criticizing their approach, per se, but I suspect even after these changes there will be continued outrage about the disproportionally attractive women staffing some booths and being paid to be chatty or even flirty.